Amplifier and tone regulator



Dec. 1939- A. J. KUHLENBECK ET AL 2,134,646

AMPLIFIER AND TONE REGULATOR Filed March 21, 1958 u MT E ym m 1 m f 3 I. .T. M 1.7 I Wu F M 5 7 MM wr frw B fit M Patented Dec. 26, 1939 UNITED STATES PATENT OFFICE Manning,

Application March 21,

4 Claims.

Our present invention relates to an amplifying and tone regulating means which may be built into stringed musical instruments, and which produces richer musical tones with greater volume than are produced with the conventional types of sounding boards.

The principal object of the invention is the provision of a pair of sounding boards rigidly secured together which vibrate in unison and 10 reproduce the music created by the strings of the instrument.

Another object of the invention is the provision of a sound chamber formed between a pair of sounding boards, with a plurality of apertures being formed through one of the boards to allow the passage of sound therethrough.

A further object of the invention is the provision of a secondary sounding board rigidly secured to a primary sounding board and providing. resonance to the sonorous sounds of the strings of the instrument when the same are struck.

A still further object of the invention is the provision of a means whereby the expansive area of the sounding board may be materially reduced without affecting the resonant qualities of the tone of the instrument.

Another further object of the invention is the provision of means for amplifying and regu- 30 lating the tone of a stringed musical instrument which increases the volume of sound, which is simple of construction, and which may be economically produced.

Other objects and advantages of the inven- 35. tion will suggest themselves in the course of the following description, and that which is new will be pointed out in the appended claims.

The several features of the invention will be hereinafter referred to in detail in the following 0, description, reference thereto being had in the accompanying one sheet of drawings, in which:

Figure l is a front elevation showing a primary sounding board mounted in a frame member and having a casting carrying music strings secured 45, thereto, such as for instance may be provided in a piano.

Figure 2 is a rear side elevation of the frame and showing the rear side elevation of a secondary sounding board.

Figure 3 is a detail vertical section through the device, taken on line 3-3 of Figure 1, and showing the relationship between the frame member, the primary sounding board, and the secondary sounding board.

55 Figure 4 is a detail section through one edge Lynn, Ind.

1938, Serial No. 197,224

of the assembled device, taken on line 4-4 of Figure 2.

Figure 5 is an enlarged detail section, taken on line 55 of Figure 4, and showing the means for rigidly spacing the secondary sounding board 5 with relation to the primary sounding board.

Like characters designate like parts throughout the several views.

In order that the construction, the operation, and the advantages of the invention may be more fully understood and appreciated, we will now take up a detailed description thereof, in which we will set forth the same as fully and as comprehensively as we may.

Referring now to the drawing in detail, I designates the frame member which surrounds the edges of the sounding board. The frame members may be the body of the musical instrument, such as for instance, the case of a piano, and is shown as a frame member in the drawing for convenience of illustrating the method by which the sounding boards may be secured in relation to the case of the instrument.

A rabbet I is formed around the inner forward edge of the frame member I with the same being adapted to receive the primary sounding board 2 which may be rigidly secured to the frame member by threaded screws, or by other suitable means. A plurality of apertures 3 are formed through the primary sounding board 2 with the apertures providing means through which the sounds from the music strings may pass to the secondary sounding board I. It will be noted that the rear side of the primary sounding board 2 is concave, making the board thinner through the-central portion than at the edges thereof. The thinner central portion causes the board 2 to be more sensitive to the sound vibrations than if the same thickness of the edges was carried over the entire area of the board. The secondary sounding board I is rigidly secured in spaced relation with the primary sounding board and supported thereby by means of the spacing posts 4. Bosses 5 are located on the forward surface of the primary sounding board 2, and the spacing posts 4 are rigidly secured on the rear side of the sounding board 2 by means of the threaded screws 5, as shown in Figure 5. The secondary sounding board I is rigidly supported and maintained in spaced relation with the primary sounding board 2 by being rigidly secured to the spacing posts 4 by means of the threaded screws H) which extend through the bosses 9 and the sounding board I. The secondary sounding board 1 has the forward face thereof concave with the rear face thereof being convex, with the result that the central portion of the same is comparatively thinner than the outer edges thereof and rendering the board more sensitive to the sound vibrations set up by the strings of the instrument.

It will be noted that each of the spacing posts 4 has a hollow portion 4' formed therein With the hollow portions causing the posts 4 to be more resonant to the sound vibrations produced by the strings of the instrument.

It will also be noted that the rear inner edges of the frame member I has the rabbet I" formed therein. formed around the outer edges of the secondary sounding board. The inner forward edges 8 are curved, as shown in Figures 3 and 4, and are provided thusly in order that the sound may not be obstructed by sharp corners.

A space is formed between the edges of the flange member 8 and the rabbet l of the frame member. The space formed between the secondary sounding board I and the rabbet l must be maintained in order to permit the sounding board I to vibrate freely without making contact with any portion of the frame member I, as any contact with the frame member I will deaden the vibrating sounds.

The cleats H are rigidly secured to the rear side of, the secondary sounding board "I in order to provide greater strength thereto.

In the drawing, a metal frame i2 is shown secured to the forward face of the primary sounding board 2 with the strut members. I? being formed integrally therewith and extending between the two members [2. A ridge l3 is formed longitudinally on the forward face of the members I2. The metal frame 12 is held in spaced relation with the forward face of the sounding board 2 by means of the spacers H6. The music strings I4 are stretched tightly over the ridges l3 by means of the threaded studs 55, with the studs being threaded into the metal frame I2 in the usual manner.

During the manipulation of the stringed instrument embodying our invention, the vibrations created by striking the music strings f4 travel through the apertures 3 and strike the secondary sounding board 7 which, being entirely supported by the primary sounding board 2 by the spacing posts 4, is vibrated by the vibrations caused by the music strings M. The apertures 3 form passages through which the vibrating musical sounds travel. It is important, as hereinbefore set forth, that there be a sufiicient space provided between the outer edges of the secondary sounding board and the rabbet l" of the frame member to allow the sounding board I to vibrate freely in order that no contact is made between the board 1 and the frame member I. It is also important that the space between the two members be kept to a minimum in order that the passage of sound therethrough will be minimized, as the passage of a great volume of sound passing therethrough destroys the sonorous resonance of the vibrations.

A forwardly extending flange 8 is.

It is to be understood that, while the invention is illustrated and described as being set in a frame, the same may be set directly into the case of a stringed instrument, with the instrument case forming the frame member therefor.

It is also to be understood that we are not to be limited to the specific form and arrangements of the parts herein shown and described, but that minor changes may be made in the construction and the arrangements of the parts, insofar as the changes may fall within the scope of the appended claims.

Having now fully shown and described our invention, what we claim, and desire to secure by Letters Patent of the United States, is;

1. In. a musical instrument having a frame member, the combination of a pair of spacedapart sounding boards one of which is secured to the frame member, the other being spaced away from the frame member and unattached thereto, each of the sounding boards having a concave surface formed in the central portion thereof with the concave surface of one sounding board facing the concave surface of the second sounding board, with the outer surface of one board being parallel with relation to the corresponding portion of the other board and with a continuous flange being formed around the outer edges of one of the sounding boards.

2. In a musical instrument having a frame member, the combination of a primary sounding board spaced apart from a secondary sounding board with the primary sounding board being rigidly secured to the frame member and with an uninterrupted space being formed between the outer edges of the secondary sounding board and the frame member, and with the central portions of the opposing surfaces of each of the sounding boards being concave and of less thickness than the outer surrounding edges thereof, and with the secondary sounding board being entirely free of the frame member.

3. In a musical instrument of the class described, a pair of spaced-apart sounding boards, each having its central portion of comparative less thickness than the outer edges thereof and with a continuous flange being formed at the outer edges of one of the sounding boards.

4. In a musical instrument, the combination of a frame member forming an enclosure and having a rabbet formed continuously in each of the inwardly directed faces of the frame, a primary sounding board rigidly secured in one of the continuous rabbets and with a secondary sounding board being connected with and spaced away from the primary sounding board, and with the outer edges of the secondary sounding board being in spaced relation with the second rabbet of. the frame member and forming an uninterrupted space therebetween and permitting the outer edges of the secondary sounding board to vibrate freely without contacting the frame member or the respective rabbets formed therein.

ALBERT J. KUHLENBECK. FORREST L. MANNING. 

